Since the introduction of the airplane by the Wright Brothers back in the early 1900s, hobbyists across the globe have been fascinated with collecting airplane related paraphernalia ranging from old pilot gear, to airplane parts like say…propellers.

Most people who decide to collect propellers do so because of their fascination with planes, but the reality is that some of them are extremely valuable—even after being detached from the plane. We’ve put together this guide on how to evaluate the worth of your airplane propeller collection.

1. Condition

The most obvious, and in some cases the most important factor, is the propeller’s condition. Ultimately, condition depends on how close the collectible is to its original state. That said, this doesn’t always mean that the more “new” an item looks the more valuable it is. In fact, more often than not, the opposite is usually true. For instance, a bullet hole from combat or a dent from a high-profile crash can actually add to its value.

What can and almost always will lower a propeller’s price tag, are alterations made to change appearances like adding varnish, removing the finish, etc.

2. Rarity

As is the case in the retail of anything—but especially antiques, an item’s value ultimately comes down to supply and demand. The harder it is to find a collectible, the more other people will be willing to pay for it.

For instance, propellers manufactured before WWI were released in very small numbers and many of them were destroyed through use or a lack of maintenance. Likewise, early propellers were made of wood and simply “not built to last” so most of them were destroyed or lost over time, therefore there are way less of these types than the later-released metal versions. Obviously these propellers will be worth much more than the more common models.

3. Identification

Any item is more valuable when you know where it’s from. Unfortunately for most collectors, a lot of propellers can’t be identified to any specific aircraft or engine. It can also be next to impossible to pinpoint the usage of a propeller to any significant person or event. That said there are a few out there with clear and indisputable characteristics that can be used to uncover a lot of historical background. In the few cases that you can, you’re likely to see a huge spike in the item’s price tag.